BOAC,
That was an uncharacteristically tetchy and provocative response to a fair question.
And, in your case, unexpectedly ill-informed.
We have all been taught to fly approaches purely on IAS in the way you describe, and many of us have used the technique on a variety of jet aircraft. It is well known, however, that a 25-knot headwind at 100ft can disappear to nothing at the threshold, particularly at night and/or when the airfield is surrounded by trees. Unlike most propeller aeroplanes, increasing the power on a jet does not in itself generate extra lift from the wing; it may provide a small vertical component of thrust. And jet-engine response is slower than pistons and turbo-props.
Airbus, for all its virtues, did not invent the concept of calculating a minimum acceptable GS on finals – they merely introduced it to line pilots in automated form on the A320 in 1988. With the advent of INS in the 1970s, giving a reliable (unlike Doppler in the 1960s) and fairly accurate GS at all speeds, the concept was soon pioneered by crews. It was first explained to me by a flight engineer on the DC10, and I wouldn't be surprised if it was an American idea. Perhaps someone will enlighten us.
The popular us-and-them attitude between Boeing and Airbus pilots is ill-considered. Both manufacturers produce conventional aeroplanes with minor differences. All their products are well-built and fly well, using similar aerodynamics.
You know only too well that aeroplanes have to operate within the laws of Newtonian physics, one of which involves inertia. Inertia is a function of GS, not IAS. But lift requires IAS. As every schoolboy knows: IAS = GS plus headwind-component (sea-level/ISA). Shortage of inertia (GS) can only be corrected by applying extra thrust; for a period of time. On a bad day at the office, that time may not be available.
I would be very surprised if no Boeing pilot on this forum has ever applied the principle of working out a minimum acceptable ground-speed. You might even consider it yourself.
Chris
Last edited by Chris Scott; 17th Nov 2008 at 00:45.
Reason: No changes since John Tullamarine's. In the penultimate paragraph, readers are warned that I loosely used the word "inertia" to mean "kinetic energy". See post #22.